(1) Field of the Invention
The present invention relates to an apparatus for clarifying and circulating hot air for treating textile fabrics. More specifically, it relates to an apparatus that circulates hot air for heat-treating textile fabrics at a high heat efficiency while clarifying the hot air.
(2) Description of the Prior Art
In a conventional heat-setting stenter or a curing apparatus for heat-treating fabric treated with a finishing agent, hot air is usually blown to the fabric at temperature of from 150.degree. C. to 230.degree. C. In this temperature range, oily and fatty components in the finishing agent on the fabric and oily and fatty substances in a lubrication oil fed to the heat-treating apparatus are gasified (vaporized and/or sublimated). The resultant vaporized substances diffuse into the hot air. When the concentration of vaporized substances in the hot air exceeds a critical value, a portion of the vaporized substances condenses in some relatively low temperature portions of the apparatus, resulting in the formation of tar-like droplets. These not only contaminate the interior of the apparatus but also fall on the fabrics to stain them.
To prevent the formation of the above-mentioned tar-like droplets, a new-type of hot air-clarifying apparatus has recently been developed. In this apparatus a portion of the exhausted hot air is heated to raise its temperature. The heated exhausted hot air is brought into contact with an oxidation catalyst to oxidize the oily and fatty substances vaporized in the hot air to modify them into water vapor and carbon dioxide gas. This type of apparatus is disclosed, for example, in Japanese Unexamined Patent Publication (Kokai) No. 56-29495.
In the conventional apparatus for heat-treating fabrics, however, both the hot air-clarifying apparatus and the hot air-circulating apparatus are arranged outside a hot air-treating chamber. The construction of the heat-treating apparatus therefore becomes complicated and results in large heat loss. When the heat-treating apparatus is divided into a plurality of compartments, furthermore, the hot air-clarifying apparatus located in the outer side must be so constructed that the hot air is uniformly withdrawn from each of the compartments and uniformly distributed again into each of the compartments after clarification. This, however, increases the cost of the apparatus and the operation.